Motor construction



Oct. 29, 1940. E Ql SCHwEn-ZER, 1R 2,219,457

MOTOR CONSTRUCTION Filed Dec; 17, 1938 5 Sheets-Sheet 1 Oct 29, 1940. E, o. scHwErrzER. JR 2,219,457

MOTOR CONSTRUCTION Filed DeC. 17. 1938 3 Sheets-Shed', 2

0f- 29, 1940, E. o. scHwEn'zER. JR 2,219,457

KOTOR CONSTRUCTION Filed Dec. 17, 193B 3 Sheets-Sheet 5 reeeaied oef. zo, 1940 UNITED STATES PATENT oFrlcE Moron coNs'raUc'noN Edmund o. senwemer, Jr., Northbrook, n1. appueeuen neeember 17, 193s, serial No. 246,326 'z claims (or 11e-m) My invention relates generally to electric motor construction, and it has particular relation to the construction of small slow speed self-starting synchronous motors.

In order to operate analternating current electric motor at a low synchronous speed it is necessary to provide a large number of poles when a source o! commercial frequency, such as a 60 cycle source, is employed. For example, when two poles are provided the motor operates at 3600 R. P. M. A four-pole motor operates at 1800 R. P. M., while a ten-pole motor operates at '720 R. P. M., and a twelve-pole motor operates at 600 R. P. M. Various arrangements of windings have been employed in the prior art in order to provide these poles. Oi course, an individual winding can be used for each pole or each pair of poles. This construction, however, is suitable principally for the larger sizes of motors and is generally impractical for small motors such as are employed for driving clocks, time switches, talking machines and other devices where a denite xed speed is required.

The so-called basket type of pole construction can be employed to provide a large number of poles. In general, this construction comprises a plurality of inter-linking spaced apart polar projections having a common magnetic return circuit around Which is positioned an energizing winding. Since this winding is relatively remote from the tips oi' the polar projections adjacent which the rotor is located, there is of course considerable leakage of magnetic flux which never iinds its way into the rotor where it could be employed for developing torque. Consequently, a motor of this type is relatively ineicient and has a relatively low power output. Because of the relatively small amount of energy required to operate motors of this type little attention has been paid to their efliciency.

There are other types of motor construction which may be employed for small low speed synchronous or sub-synchronous motors. However, they are generally relatively ineilicient or they v4&5 lack sufficient power to drive an appreciable load such as the load which is encountered in driving the turn table of a phonograph.

Accordingly, the objects of my invention, generally stated, is to provide a low speed high power 50 self-startingv alternating current motor which shall be simple and eilicient in operation and which can be readily and economically manufactured and assembled.

An important object of my invention is to pro- 55 vide a large number of poles :or an alternating current motor by employing a single winding so arranged that it creates the poles substantially at the place where the resulting ux is employed for developing torque.

Another important object of my invention is to l substantially increase the power output of an alternating current motor having a large number of poles that are created by means of a single winding.

Still another important object of my invenl0 tion is to generate flux 'at each pole of an alternating current motor having a large number of poles by means of a winding common to all of the poles. y

Another object of my invention is to operate a l5 motor at a relatively low synchronous speed by employing a single winding linking a large number of poles.

Still another object oi my invention is to so arrange the single winding of an alternating cur- 20 rent motor which energizes a large number o! poles in such manner that it may be manufactured relatively simply, such as by a punch press operation.

A further object of my invention is to create a 25 shifting magnetic field in an alternating current motor of the type described herein.

Still another object of my invention is to provide for self-starting a low speed synchronous motor of the type described herein. 30

A still further object of my invention is to electrically shift the magnetic field in a motor of the type described herein without requiring the use of shading coil means.

Still another object of my invention is to gen- 35 erate a shifting polyphase magnetic ileld in a motor of the type described herein through the use of time and space phase displaced alternating currents.

A further object of my invention is to generate 40 a synchronous polyphase magnetic field in a moltor of the type described herein by the interaction of a pair of windings each differently linking the polar projections of the motor and energized by time phase displaced alternating currents.

Other objects of my invention will in part be obvious and in part appear hereinafter.

According to my invention I provide an alternating current motor having a large number of polar projections each of which is individually energized by a single turn of a common winding in such manner as to create alternate poles of opposite polarity. The polar projections are formed, of course, of magnetic material and are uniform- 1y spaced about a rotor. The polar projections are linked by a single turn of a wave winding which is energized from a suitable source of single phase alternating current. Since only a single turn is employed, the' voltage applied thereto is relatively low and the current flow therein is relatively high. To obtain this voltage and current relationship the single turn of the winding is preferably arranged to constitute an extension of a secondary winding of a transformer, the primary winding of which is connected to a suitable source of alternating current such as a 110 volt, 60 cycle source. A disc type of rotor when brought up to the synchronous speed determined by the number of poles and the frequency will continue to rotate at this speed.

In order to provide a motor having self-starting characteristics, the polar projections may be formed in pairs having the wave winding linking the pairs of polar projections so that there will be alternate pairs of poles of opposite polarity. I'he corresponding pole of each pair of poles is shaded so that a shifting magnetic field is created which is effective to bring the rotor from standstill up to synchronous speed.

According to another embodiment of the invention two wave windings are provided and are arranged to interlink different combinations of the polar projections. The two windings are connected for energization to time phase displaced sources of alternating current with the result that a rotating magnetic field is created by the interaction of the time and space phase displaced iiuxes that are generated as a result of the interaction of these two windings.

In order to facilitate manufacture of the motors of the type described herein the stator windings are so constructed that they may be formed by a simple stamping or punch press operation. This is possible because only a single turn wind- C ing is employed.

For a more complete understanding of the nature and scope o1. my invention reference may be had to the following detail description taken in connection with the accompanying drawings, in which- Figure 1 is a view in side elevation of one embodiment of a' motor constructed in accordance with the present invention;

Figure 2 is a bottom plan view'oi' the motor shown in Figure 1;

Figure 3 is a plan view of the stator of the motor shown in Figure 1;

Figure 4 is a detail sectional view taken along the line 4-4 of Figure 1;

Figure 5 is a view in side elevation of another embodiment of the motor constructed along the lines of the motor shown in Figure 1;

Figure 6 is a detail sectional view at an enlarged scale taken along the line 6 5 of Figure 5;

Figure '7 is a view in side elevation of a polyphase motor constructed in accordance with the present invention together with the circuit connections, the core structure of the transformers being shown in section in order to more clearly illustrate the invention;

Figure 8 is a bottom plan view of the motor shown in Figure 7;

Figures 9 'and 10 are views in side elevation of the windings forming a part of the stator of the polyphase motor shown in Figure 7; and

Figure 11 is a Vector diagram of the flux relationships which exist in the polyphase motor shown in Figure 7.

Referring now particularly to Figures 1 and 2 of the drawings, it will be observed that the reference character I5 designates generally a motor having a rotor I6 which may be formed of a disc of magnetic material. The disc I6 is surrounded by a stator, shown generally at Il, which includes a plurality of polar projections I8 in the form of pms of magnetic material that are suitably secured, as by riveting, to a ring I9 of magnetic material. A cross member may be secured to the ring I9 for supporting a shaft 2| on which a hub 22 of the rotor I6 is mounted for rotation.

With a view to energizing the polar projections I8 a single turn wave winding 25 is provided as a part of the stator I'I. As shown more clearly in Figure 3 of the drawings, the winding 25, which is preferably formed of copper, is provided with uniformly spaced apertures 26 for interfltting with the polar projections I8 and through which they project as illustrated more clearly in Figures 2 and 4 of the drawings. Since it is desired to have the winding 25 link pairs of polar projections I8, radial slots 2l are provided extending outwardly from every other pair of apertures 26 while similar slots 28 extend radially inwardly from the other alternate pairs of apertures 26.

An additional slot 29 is provided to separate the ends of the winding 25 so that the current nowing therethrough follows the sinuous path indicated by the broken line 30 at some instant in a cycle of alternating current. With the current flow as indicated by the broken line 30, the polar projections I8 will have the polarities as indicated thereon. For each pair of north poles there is a corresponding adjacent pair of south y poles. Since there are ten pairs of poles the synchronous speed of the motor and the speed at which the rotor I6 operates is 720 R. P. M.

It is of course desirable to have the motor I5 capable of self-starting so that it is unnecessary to provide external means for bringing the rotor I6 up to synchronous speed. For this purpose a shading ring 33 is provided having apertures 34 therein which are .so spaced as to permit the polar projections I8 to project therethrough, as is more clearly shown in Figures 2 and 4 of the drawings. Since it is desirable to shade only one -polar projection of each pair, every other aperture 34 is provided with a slot 35, which, as shown in Figure 1, may extend radially inwardly. In this manner one polar projection of each pairvof poles is unshaded while the other polar projection is shaded. For example, the polar projection I8u with which one of the slots 35 is associated is unshaded, while the other polar projection I 8E of this pair of polar projections is shaded since it is entirely surrounded by a portion of the shading ring 33. The shading ring 33 is preferably formed of copper.

In order to reduce the flow of circulating currents in the shading ring 33, one of the slots 35 may be extended through to the outer periphery as indicated at 36, thereby providing an incomplete circuit around the shading ring 33.

In'the construction of the motor I5 it will be noted that the winding 25links each pair of polar projections I8. Each pair of poles is substantially equally well supplied with magnetic nuxsince the same current flows past each pair of poles and therefore each pair of poles has the same number of ampere turns applied to it. This is in contra-distinction to the so-called basket construction in which the ampere turns of the energizing winding are, in eifect, divided among all Qf the poles rather than having all of them availgsle for each pole or pair of poles as the case may The winding 25 may be energized from a suitable source of alternating current. Since this notching the polar projections IB, ligure 2, the same result can be obtained. The pins forming thepolar projections 5l are suitably secured, as by riveting, to a ring 51 of -magnetic material. IA

I1 for carrying thereon a shaft or pin 50 on which a hub Sil carrying the rotor 52 rotates.

Inl order to energize the polar projections 5l a single turn wave winding 6I is provided havdrawings, the wave windings 80 and 8i form continuations of secondary windings 82 and al, respectively, which in turn form parts of transformers Il and 8l, respectively. Primary windwinding is a single turn winding it is necessary ing apertures and slots therein arranged as shown 6 that a relatively large current flow through it in Figure 3 of the drawings for a similar windin order to create the necessary magnetic field ing 25. The sluiting magnetic ileld vis created for operating the rotor Il. Because of the large by means of a shading ring 62 that is lessentially section of copper forming the winding 2l a relathe same as the shading ring 33 illustrated in tively low voltage is required to cause this heavy Figure 1 of the drawings. In Figure 5 the l0 current to flow. These requirements naturally radial slots in the shading ring 82 are not shown lend themselves to the use of a transformer for because the slots in the wave winding Il are energizing the winding 2l, although it will be unshown by broken lines and might be confused derstcod that the winding 2i may be directly with the Slots in the shading ring l2. connected to a source of alternating current. Any suitable source of alternating current may l5 As a practical expedient. the ends of the windbe employed for energizing the wave winding Si. ing 2l are connected by conductors Il and 4l As shown in Figure 5, the ends of the winding to a single turn secondary winding 4I of a 8l are spaced as indicated at BI and conductors transformer shown generally at I2, having a ll and 05 extend therefrom for connection to a primary winding Il and a magnetic core M suitable source l0 of alternating current, such as a0 which links both the primary and secondary a 60cycle source. .J windings, as illustrated. The primary winding By turning the ends 55 of the polar projec- 43 may -be connected by conductors 45 and 40 tions I4 inwardly as shown in Figures 5 and 6 of to la source I1 of alternating current. such as 4the drawings and forming the faces I8 so curved a 60 cycle 110 volt source. as to conform to the curvature of the periphery 25 It will be observed that the winding Il formof the rotor l2, the efilciency of the motor 5i is ing a part of the stator I1 really constitutes an somewhat increased over that of the motor i5 extension of the secondary winding li of the because of the decrease of leakage flux in the transformer I2. Obviously, the windings 25 former. Moreover, as indicated, this arrangeand 4I interconnected by the conductors 3l and ment of the outer ends. of the polar projeci0 l0 may be formed from a single piece of contions 5I tends to center the rotor 52 at a preducting material such as copper. The ari'angedetermined position along the shaft Il thereby ment of these windings is such that they may be making it unnecessary to provide a thrust bearstamped or punched out of plate copper by a ing. single operation, or, if necessary, repeated op- The space factor for the windings 25 and Il 85 erations, to form them into the shapes shown is considerably less than the space factor for with the apertures and slots therein as illusordinary windings employing a number of turns trated. a e of insulated wire. In the first place no insula- While the Secondary Winding l 0f the trnstion between turns is required since only a single former l2 is shown as being in the same plane turn ls employed.l In the second place, since a 5 8s the Winding 25 0f the $8301' l1. it Will be 0bsingle turn of solid cross section is used there is ViOilS that they may be Ditined-i riht 3118198 of course no waste space as occurs between the i0 each other 0r in Parallel Planes if ii'l is deturns of a winding made up of a number of turml sired to provide a more compact construction. of insulated wire, For illustrative purpom, however, the construc- Referring new particular-1y to Figures 'I andf8 a tion and novel features are more clearly illusof the drawings, it will be observed that the re!- tried by showing the windings 25 and 4|. in the erenc'e character 1i designates generally a motor same plane. l constituting still ,another embodiment of my in- Referring now particularly t0 Figures-5 and 6 ventio'n. The motor ll is in ei'iect a polyphse 0f the drawings, it Wm. be Observed met another motor in which a rotating magnetic field is c re- 50 embodiment of the invention is illustrated. The ated by means ef time and space phase dismotor shown generally at Il is somewhat similar placed magnetic fields generated by separate in construction to the motor illustrated in Figwindings, The motor 1i comprises a disc type of ures l, `2, 3 and 4 and described vhereinbeiore. reim-'12 that is surrounded by e, stator, shown It comprises a disc type of rotor 52 that is surgener-ily at 13, 55 -rounded by a stator, shown generally at 53. The stator 13 eempriseg a plurality of polar As shown more clearly in Figure 6 of the drawprojections 1| in the form of pins of magnetic ings, the Stato? 53 is Provided with plurality material that are secured to and carried by 8 of polar projections 54 in the form of pins of ring 15 iikewise formed of magnetic material. magnetic material the Outer ends l5 0f which A suitable support member 1l is carried by the 50 are curved or tur'ned radially inwardly toward ring 1s and 1t in turn can-lee a shaft or pm 11 the rotor t2.r The: surfaces 58 'of the polar Proon which e hub 1s cr the rotor 'n rotates. iections 54 adjacent the periphery of the rotor with e, view to energizing the polar projec- 52 arecurved to conform to the curvature of the tions 1l two single turn wave windings l0 and rotor so that the length of the air gap will be at Il .are provided and are insulated from each e5 a minimum, with the result that the leakage other by any suitable means such as by coating iiux is materiallyreduced. Another advantage them with insulating material such as varnish, of thefinwardly turned ends il is to obvlate end shellac. etc. Since the voltage is very low, the thrust of the rotor 52 since, in this arrangement, normal oxide coating may be sufllcient. As it centers itself in alignment therewith. ny shown more clearly in Figures 9 and 10 0f the 7o ings Il and l1 are provided for the trans- 75 Il support member 5I may be secured to the ring ormers 84 and 85. The primary and secondary windings of the transformers are linked as illustrated by cores 88 and 89 of laminated mag` netic material.

Since it is desirable to energize one of the primary windings 86 or 81 with alternating current that is displaced in time phase from that with which the other primary winding is energized, as shown in Figure 7, the primary Winding 86 is connectedthrough a capacitor 92 and across conductors 93 and 94 which are energized from a suitable source 95 of alternating current. The primary winding 81 is connected directly to the conductors`93 and 94 so that the current in it lags behind the current in the primary winding 86 by approximately ninety degrees.

Referring to the wave windings and 8| shown in Figures 9 and 10, it will be observed that the radial slots are arranged differently in each of them so that each winding interlinks the polar projections 14 in diierent manners. This arrangement is desired in order to obtain a space phase relation between the fluxes generated by the wave windings 80 and 8|.

For descriptive purposes the letters A, B and C in Figure '7 are applied to the polar projections 14. The same identifying characters are applied to the apertures in Figures 9 and 10 which correspond to these polar projections.

It will be observed that the arrangement of the radial slots in the wave winding 80 of Figure 9 is such that the current ows along the path indicated by the broken line 96. This current path then passes around the A and C poles oi' the group of poles A, B and C in one direction and around the B pole of this group in the opposite direction. As a result, at a given instant the poles A and C may be north poles while the pole B is a south pole.

Now, referring to Figure 10, it will be observed that the radial slots are provided in the wave winding 8l in such manner that the current fromthe secondary winding 83 ows along the path indicated by the broken line 91. Considering any group of poles A, B and C, this current path passes around the poles A and B together in one direction and around the pole C in the opposite direction. Thus at a given instant the poles A and B may be north poles while the pole C is a south pole.

Because of the provision of the capacitor 92 the current owing in the wave winding 80 leads the current flowing in the winding 8|. Because the current flowing through the wave winding 80 links the polar projections in a dierent manner than does the current flowing through the wave win'ding 8|, the magnetic fields resulting around the stator 13 are displaced in time and space so that in eiect a rotating field is provided.

As shown in Figure 1l, this relationship of the magnetic fields may be represented vectorally. Considering iirst the magnetic field which is generated by the current-flowing along the path 91 in the winding 8| of Figure 10, the magnetic ux created at the poles A and B may be represented by the vectors OAi and OB; which are superimposed one on the other. "Ihe flux generated at the C pole 'may be represented by the vector C1. These vectors are4 oppositely related as shown since the current owing along the path 91 generates a magnetic field in the poles A and B in one direction while it generates a magnetic eld in the pole C in the opposite direction.

Referring now to the current flowing along the path 96 in the wave winding 8U of Figure 9, it

will be recalled that this current leads the current owing along the path 91 in the wave winding 8l. In the winding 80 the current along the path 96 interlinks the poles A and C so that the magnetic ux thereat may be-represented by the `outwardly while the slots in the winding 8| 'associated with the A and B poles extend radially inwardly. The current ow around the poles A and C in the winding 80,1s less ellective in producing magnetic ux in these'poles than is a like current in producing magnetic ux at the poles A and B in the winding 8|. In like manner the vector OCr representing the flux generated at the pole C by the winding 8| is somewhat shorterr than the vector OB'.` representing the ux which is generated at pole B by the winding 80.

In further explanation of the difference between the iluxes generated at the A and B poles in Figure 9, as represented by the vectors OA: and CB2 in Figure l1, it is pointed out that the B poles are surrounded by the single turn wind` ing 80 while the A poles are outside of this winding. At a given instant when the current now in Winding 80 is in a clockwise direction the upper ends of the B poles will form south poles. At the same instant the corresponding ends of the A poles will form north poles. However, because ofvl the proximity of the relatively large amount of ux -within the single turn winding 80 to the A poles, there is a differential or demagnetizing effect which results in the A poles, inthe particular case in question, being somewhat weaker than the B poles.

As shown in Figure 11, the vectors may be combined to produce the vectors OA, OB and OC which, while not symmetrically arranged, they produce the eiect -of a rotating magnetic eld that is somewhat the same as is generated by a distributed winding of a three phase alternating current motor. The well known advantages of a three phase motor construction -are then obtained by properly combining the two windings 80 and 8| with dierent pole combinations. A relatively large starting torque isprovided since the resultant fluxes are fairly widely spaced apart. Since shading coils or rings are not employed to obtain the time and space displaced iiuxes, the eilciency of -the polyphase construction is considerably improved. Then too, it is possible to materially exceed the usual 20 to 30 phase shiftto which the shading construction is of course limited. Therefore a more uniform torque can be developed.

Although eighteen polar projections 14 are illustrated in the motor construction shown in Figures 7 and 8, they are so related as to produce in effect six pairs of poles or twelve poles, whereby the rotor 12 is operated at aspeed of 600 R. P. M. when the source is a 60 cycle source. It will be noted that only three polar projections 14 are required to obtain a north and south pole combination in the motor 1| While four polar projections I8 or 54 in Figures 2 and 6, respectively, are required. This is due to the fact that in the one construction the polar projections 14 are 75 linked by windings energized by time phase displaced currents while in the other construction only a single winding is directly energized and reliance is placed on the shading rings to lag the flux and provide a time and space phase relationship between parts of the fluxes.

It will be obvious that the arrangement of the transformers 8l and 85 may be different from that shown. For illustrative purposes, however, these transformers have been shown in such relation to the motor 'li that the secondary windings I! and 83 lie in the planes of the windings 80 and 8|. Obviously, the secondary windings 82 and 83 can be turned at right angles to the positions shown in the drawings so that the cores 88 and l! will be in the same or parallel planes. When ysuch a construction is employed the amount of magnetic material for the cores can be reduced by combining certain parts of the magnetic circuit for both of the sets of primary and secondary windings.

Instead of employing the capacitor 92 for shifting the time phase relation of the currents in the windings l and 8|, the construction of the primary windings 86 and 81 and their associated cores 8B and 89 may be such as to provide the desired relationship. For example, as indicated in Figure 8 of the drawings one of the primary windings may have a relatively small number of turns and the associated magnetic circuit may be relatively good while the other primary winding may have a relatively large number of turns and the associated magnetic circuit may be relatively poor, both primary windings, however, having the same number of ampere turns. Combinations of these relationships may be employed with the capacitor 92, if desired.

Since certain further constructions can be made without departing from the spirit and scope of my invention, it is intended that all matter shown in the accompanying drawings or described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

y 1. An electric motor comprising, in combination, a rotor; a stator cooperating with said rotor and including a plurality of pairs of l,polar projections disposed in uniform spaced relation, a

ltransformer including a single turn secondary winding, a single turn winding constituting an integral extension of said secondary winding embracing said pairs of polar projections in 'a sinuous manner to create alternate pairs of poles of opposite polarity, and shading means cooperating with the corresponding polar projection of each pair of polar projections for creating a shifting magnetic ileld whereby the motor is selfstarting; a primary winding for said transformer adapted to be connected to a single phase source of alternating current, and a magnetic circuit linking said primary and secondary windings.

2. An electric motor comprising, in combination, a rotor; a stator cooperating with said rotor and including a plurality of pairs of polar projections disposed in uniform spaced relation, a platelike single turn winding having spaced apertures therein for interiitting with said polar projections, adjacent pairs of apertures opening radially outwardly and inwardly to create alternate pairs of poles of opposite polarity, and a platelike shading ring having spaced apertures therein for interfltting with said polar projections and arranged and adapted to cooperate with thecorresponding polar projection of each pair of polar projections for creating a. shifting magnetic field whereby the motor is self-starting; and circuit means for connecting said winding means to a shingle phase source of alternating current.

3. An electric motor comprising, in combination, a rotor; a stator cooperating with said rotor and including a plurality of polar projections disposed in spaced relation, and a pair of single turn windings each embracing different combinations of said polar projections in a sinuous manner; and means for energizing said windings with alternating current.

4. An electric motor comprising, in combination, a rotor; a stator cooperating with said rotor and including a plurality of polar projections disposed in spaced relation, a pair of transformers each including a single turn secondary winding, and a. pair of windings each embracing different combinations of said polar projections in a sinuous manner, each of said windings constituting an integral extension of one of said secondary windings; a primary winding inductively related to each secondary winding, and means for energizing said primary windings with alternating current.

5. An electric motor comprising, in combination, a rotor; a stator cooperating with said rotor and including a plurality of polar projections disposed in spaced relation, and a. pair of single turn windings each embracing diiferent combinations of said polar projections in a sinuous manner; and means for energizing said windings with time phase displaced alternating currents whereby a shifting magnetic ileld is generated and the motor is self-starting.

6. In a dynamo-electric means, in combination, a. plurality of pole members in groups of three'comprising A, B and C pole members, a iirst single turn winding embracing in a sinuous manner the A and C pole members in one direction and the B pole member in the opposite direction, and a second single turn winding embracing in a sinuous manner the A and B pole members in one direction and the C pole member in the opposite direction.

7. In a dynamo-electric means, in combination, a plurality of pole members, and a pair of single turn windings disposed to be energized with time phase displaced alternating currents, said windings embracing said pole members in a sinuous manner to generate a three phase shifting magnetic ileld.

EDMUND O. SCHWEITZER. Jl. 

